Case stacking and unstacking machine



'7 Sheets-Sheet 1 A rroAwe-rs Sept. Il, 1962 R. J. RUSSELL ETAL cAsr:sTAcKING AND uNsTAcxING MACHINE FileaJune 24. 1959 Sept. 1l, 1962 R. J.RUSSELL ETAL CASE sTAcKING AND uNsTAcxING MACHINE Filed June 24, 1959 '7Sheets-Sheet 2 a L ev n. A 4 mma m m Jn N P I .A 31.! 3 f d M C MM MM/m0 M W 6 3 4 .y M M F Am 9 G 0./ c. u a l IJ III /f l O a SePt- 11, 1962R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE Filed June 24, 1959 '7 Sheets-Sheet3 5 on ipa/92.

Sept'. 11', T962? R. J. RUSSELL ErAL 3,053,402

CASE STACKING ND UNSTACKING MACHINE Filed June 24', 1959 7 Sheets-Sheet4 'ama/m a Puls/6 Sept. l1, 1962 R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE Filed June 24, 1959 7 Sheets-Sheet5 7k;` Jl iii 74 i E E INVENTOR:

@056er a. .easafzL fill@ By on/Alea A. ron/fs Sept. 1l,

Filed June 24, 1959 R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE 7 Sheets-Sheet 6 @wd/0M ATTO/wysSept 11, 1962` R. J. RUSSELL ETAL 1 3,053,402

CASE STACKING AND UNSTCKING MACHINE IN VEN TOR' Patented Sept. 11, 19623,053,402 CASE STACKING AND UNSTACKING MACHINE Robert J. Russell,Northl'ield, Mass., Joseph F. Cella,

Brouxville, N.Y., and Edward A. Towles, Northampton, Mass., assignors toCella Machinery Inc., New York, N.Y., a corporation of New York Filed.lune 24, 1959, Ser. No. 822,602 4 Claims. (Cl. 214-6) This inventionrelates to machines for stacking and/ or unstacking articles such asboxes, milk cases, or the like. The invention as disclosed herein isadapted to receive successive articles to be stacked from a line of sucharticles moving along on a conveyor, Istack the articles, and dischargethe stack from the machine. In the alternative, a machine embodying theinvention as disclosed herein is adapted to receive successive stacks ofarticles from a line -of such stacks moving on a conveyor and unstackeach stack, discharging the unstacked articles from the machine.

A primary object of the invention is the provision of a stacking and/orunstacking machine which is fully automatic in oper-ation, is o small,compact size in relation to the operation it performs and the articlesit handles, which may be fabricated at a low cost, and installed with aminimum of disturbance of the article conveyors with which it is to beassociated.

Another object of the invention is the provision of a machine which willstack boxes or cases moving one behind the other on a conveyor whichruns through the machine by picking successive cases upwardly off theconveyor to place each case so removed beneath a case previously removeduntil a stack of `determined height has been accumulated, and thereafterplace the stack back on the conveyor from which the cases wereoriginally drawn so that the stack may be discharged from the machine.

Another object of the invention is the provision of an unstackingmachine adapted to receive successive stacks Iol boxes or cases from laconveyor running through the machine and which will successively removethe lowermost case of the stack land place it on the same conveyor bywhich the stack entered the machine so that the case may be dischargedfrom the machine, and automatically repeat the operation until all ofthe cases of successive stacks have been discharged from the machine.

Another object of the invention is the provision of a case stackingmachine which includes a reciprocating case elevator operable to raisesuccessive cases olf of a case conveyor and place them on cooperatingcase supporting means which supports each case spaced above the conveyora distance exceeding the height of the foillowing case, with `the meansfor supporting the cases above the conveyor being automaticallyretracted to place the cases so supported on the folowing case as thesame is raised by the elevator, and with such supporting means beingextensible to support the last raised case and those resting thereuponto all-ow the elevator to return to a lowered position preparatory toraising the next following case.

Another object of the invention is the provision of a case unstackingmachine which includes an elevator for raising `a stack of cases oi of acase conveyor with a case holding `device operable synchronously withthe elevator to support the stack of cases above the lowermost case andhold ysuch stack elevated as lthe elevator moves downwardly to place thelowermost case lon the conveyor, and which stack holding device willrelease the stack when the elevator returns upwardly from the conveyorafter a previously unstacked case has been discharged from the machineto allow the elevator to lower the stack the height of the bottom caseand thereafter again support the stack as the elevator lowers the bottomcase to the conveyor with the cycle repeating until all of the cases ofthe stack have been deposited by the elevator on the conveyor anddischarged from the machine.

Another object of the invention is the lprovi-sion of an 'articlehandling machine which is selectively operable to stack cases at onetime and unstack cases at another time, with whichever operation desiredbeingsele'cted by the machine attendant. While hereinafter the:invention is described `and claimed in connection with case stackingand un-stacking, it should be understood that the word case is usedbroadly to describe boxes, crates, and the like.

Other objects, advantages, and meritorious features will more fullyappear from the specification, claims, and accompanying drawingswherein: A g

FIG. 1 is a top view of a mach-ine embodying the invention;

FIG. 2 is va cross sectional view taken on' the line 2-2 of FIG. l;

FIG. 3 is a cross sectional view taken on the line 3 3 of FIG. 2;

FIG. 4 is a cross sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a schematic view showing the relative positions between casesduring the stacking operation;

FIG. 6 is -a schematic view showing the relative positions of casesduring an unstacking operation;

FIGS. 7 and 8 are schematic views of the electrical control `systemofthe machine, FIG. 7 relating primarily to that portion of the systemwhich is operative when case stacking is selected, and FIG. 8 relatingto that portion of the system which is operative when unstacking isselected.

The machine described herein is particularly well suited for thestacking or unstacking of milk bottle cases and when used as a stackerin a dairy, is positioned over a case conveyor carrying lled cases awayfrom the machine which deposits the milk bottles in the cases. In theevent the machine is to be used as an unstacker, it is positioned overthe case conveyor somewhere ahead of the station at which the emptybottles are removed from the cases, or in the event of the cases beingused for packing paper cartons of milk and where the cases are returnedempty to the dairy, the machine would be positioned ahead of the casewashing machine. Where the machine is to be used in a dual capacity,i.e., at one time as a stacker and at :another time as an unstacker, theconveyor system with which it is associated will have a single conveyorcommon to the machine which is capable of operation in oppositedirections and during operation in one direction will deliver stacks ofcases to the machine for unstacking, and when operated in the otherdirection will deliver single cases` to the machine for stacking.

The machine disclosed herein stacks and unstacks cases from the bottom.In other words, rather than placing successive cases one on top of theother as would normally be done by hand in building a stack, thismachine places successive cases one beneath the other to Ibuild thestack. In unstacking, the machine withdraws successi-ve cases from thebottom of a stack rather than withdrawing the cases from the top of theStack. The unstacking operation is essentially merely the reverse of thestacking operation with certain variations,

The machine as disclosed herein has been designed for use with what istermed an in-floor conveyor, which type of conveyor is coming intowidespread use in the dairy industry. The machine is simply placed inthe door through which the in-floor conveyor travels with provisionbeing made to allow the case lifting fingers of the case elevator todrop below the case supporting surf-ace of the conveyor.

A typical installation for handling conventional milk bottle cases of asize approximately 14" long by 111/2" wide, would occupy a space roughly3'4 square centered over the case conveyor and with the height of themachine being substantially equal the height of the stack of cases to behandled. The machine, generally indicated at 20, is adapted to rest onthe floor over which the cases are conveyed by the case conveyor 22. Thecase conveyor serves to deliver cases to and discharge cases from themachine, and is a conventional double chain conveyor. The cases rest onthe chains and as the chains move, the cases are frictionally carriedtherewith. The machine has a frame comprising, as best shown in FIGS. land 2, four upright channel members 24, 26, 28, `and 30, which aresecured by angle plates 32, 34, 36, and 38 to a pair of lloor plates 40and 42 disposed on opposite sides of the case conveyor 22. The lloorplates may in turn be secured to the floor of the building as by boltsor the like 44. Disposed at opposite sides of the conveyor 22 andcarried by this frame is the vertically shiftable case elevating andlowering mechanism indicated generally at 46, as well as the caseretaining mechanism which includes the supporting mechanism 48 and thecase holding or clamping mechanism 50, the latter being operative onlyduring unstacking.

Tie plates 52 are secured to uprights 24 and 26 as shown in FIGS. 1 and2, and a similar tie plate, not shown, rigidilies uprights 28 and 30.Another tie plate 54 extends across conveyor 22 spaced thereabove so asnot to interfere with case travel on the conveyor and is secured betweenand to the upper ends of uprights 26 and 30 to tie the upper ends of theframework on opposite sides of the conveyor together.

Assuming the machine is to be used for stacking cases, the cases C enterthe machine on the case conveyor 22 in the direction of arrow S in FIG.1, one behind the other. As the leading case passes between uprights 26and 30 and its leading edge is about one-half the way through themachine, it strikes the arm 56 of switch LS-l, which in turn activateslluid pressure cylinder 58 to withhold the advance of those casesfollowing the leading case. Cylinder 58 is pivotally connected at 60 toa bracket 62 secured to upright 30 and at the opposite end has a pistonrod pivotally connected at 64 to a case stop 66, in turn pivotallysupported by a bracket 68 secured to upright 30. As LS-l is tripped, itcauses pressurization of cylinder 58 to pivot the stop 66 from the solidto the phantom outline position in which the stop presses against thecase next following the leading case and withholds its movement.

The leading case continues to travel until it comes into abutment withthe extended case locators 74 and 76. The case locators are a pair ofabutments or stops, one at each side of the path of case travel, whichare extensibly and retractibly carried by bearings 78 and 80 secured touprights 28 and 32, and are actuated for such movement by fluid pressurecylinders 82 and 84, also mounted in any convenient fashion on uprights28 and 32. As will `hereafter appear, these locators remain in theextended position during the stacking operation and retract to let astack pass out of the machine on conveyor 22 at the end of the stackingoperation.

When the case actuates switch LS-l, such switch initiates a time delayrelay 'fR-1, which relay measures a determined interval of time suicientto allow the case to reach the locators 74 and 76 and then causes thecase elevator 46 to start its rising oper-ation to lift the case off theconveyor to a height above that of the following cases. The caseelevator includes four case lifting lingers indicated at 118, 118 120,and 120,1, and hereinafter more fully described. As the case rises, casesupports 86, 86a, 88, and 88a above it retract, allowing any casessupported thereon to be placed on the ascending case and to allow theascending case to pass by the supports. When the ascending case reachesa position above the supports, they are again extended, the elevatorreverses its travel, and during descent places the case on the supportsand continues back down to its starting position to repeat theoperation.

The elevator comprises a pair of identical mechanisms on opposite sidesof the conveyor 22 and disposed between the uprights of the frame. Eachsuch mechanism includes a pair of vertical rods 96 and 98 for onemechanism, and and 102 for the other. Hereafter a description of onesuch mechanism will sullice for both. The rods are mounted on theupright frame members in blocks 99 and 101 secured to the frame membersand to opposite ends of the rods. &lpported for vertically slidablemovement on the rods is an elevator carriage which includes a pair ofvertical members 104 and 106 having rod bearings 108, 110, 112, and 114secured thereto and received upon the rods, with a horizontal crossmember 116 extending between and secured to the upper ends of members104 and 106. Secured to the lower end of the carriage and specilicallyto the lower ends of members 104 and 106 are the elevator lingers 118and 120 which, as will be noted with respect to linger 118 in FIG. 3,extend beneath the path of travel of a case on conveyor 22.

The elevator lingers are raised and lowered by a fluid pressure cylinder122 which acts upon the elevator carriage. Cylinder 122 is secured atthe lower end to the lloor plate 42, and at the upper end has a pistonrod 124 connected to the cross piece 116 of the carriage. Uponpressurization of the cylinder at the lower end the lingers are raised,While pressurization at the opposite end causes the lingers to belowered. The complemental elevator fingers 118a and 120a on the oppositeside of the case conveyor cooperate with lingers 118 and 120 to raisecases off the conveyor or replace elevated cases on the conveyor. Thelingers come up simultaneously beneath the bottom of the cases to raisethem from the conveyor.

The case supports 48, which hold the previously raised cases elevated assucceeding cases are brought up to be stacked beneath those held by thesupports, comprise the aforementioned four lingers 86, 86,1, 88, and88a, which are mounted for extensible and retractible movement with twoof the fingers disposed on each side of the conveyor 22 and yat a heightthereabove so that they will clear the top of the highest case which maybe stacked or unstacked by the machine. A description of one pair oflingers as shown in FIGS. 3 and 4 will suffice for both pairs. Thefingers are carried by sleeve bearings 126 and 128 slidably mounted onrods 130 and 132, which are carried at opposite ends by vertical plates134 and 136 upstanding from and secured to the iloor plate 42. A crossmember 138 extends between and is secured to the lingers behind thesleeve bearings to prevent revolution of the lingers on the rods. Thefingers are disposed just beyond the edges of vertical plate 134 andreciprocate from a retracted position shown on both sides of conveyor 22at 86 and 86 in FIG. 6 and an extended case supporting position shown at86 and 86 in FIG. 5. A lluid pressure cylinder 139 suitably supported atone end on an angle member 141, secured to vertical plate 136, andhaving a piston rod 140 connected to cross member 138, is opera tive toextend and retract the pair of lingers 86 and 88, while a similarcylinder is operative to accomplish the same with the other pair oflingers 88 and 88a.

Considering FIGS. 3 and 5, the sequence of operations in stacking casesmay be readily comprehended. Assuming a case C-2 is supported by thesupporting lingers, of

v which two are shown in FIG, S at 86 and 86a, and another case rests onthe case conveyor 22 and is in abutment with the locators 74 and 76,which are in the extended position shown in phantom outline, asmentioned herebefore the case has actuated LS-l and after a short timedelay the elevator starts its upward movement raising the elevatorlingers, of which two are shown at 120 and 120,... The lingers pick caseC-1 off the conveyor and raise it toward the position occupied by caseC-2. lust before the upper edge of case C-l strikes the Icase supports86 yand 86a, switch LS-3, mounted on the upright frame member 30, isactuated by an adjustable trip 142 mounted on the elevator member 104.Actuation of switch LS-3 causes the case supports 86 and 86a to beretracted to the position shown `in FIG. 6. Because case C-1 is movingrapidly upwardly and the supports are withdrawn from beneath case C-2when only substantially one-half inch or less exists between the twocases, case `C-2 will `drop only slightly, perhaps one-quarter inch,before it seats upon case `C-1. With case C-2 now stacked on case \C-1,both cases are elevated through the remainder of the stroke of cylinder122. At the top `of the stroke of cylinder` 122, and assuming a fullstack has not been accumulated, switch LS-4 is contacted by anadjustable trip 144 mounted on the elevator carriage and this reverselypressurizes the cylinders 139 to extend the case supports 86, 86a, 88and 88a. When the case supports yare extended, switch LS-7, mounted onthe bracket 141 and having a switch arm in contact with the cross member138 w-hen the supports are retracted, is actuated to cause the elevatorto lower cases C-l and C-2 to the supports, upon which they are placedas the elevator returns to its starting position shown at 120 and 120,lin FIG. 5.

As cases C-1 and @-2 are now carried by the supports, another case mayenter the machine for stacking. As the elevator reaches the bottom 4ofits movement, it trips switch LS-S mounted on the oor plate 42, which inturn reversely pressurizes case stop cylinder 58 to retract the stop 66away from the case it is holding, allowing such case to enter themachine and trip switch LS-1 to repeat the abovedescribed cycle.

As the stack of cases increases in height through repetition of thecycles, the machine automatically stops the stacking after a determinednumber of cases have been stacked, and the stack is thereafter sent outof the machine on conveyor 22. Secured to the machine -frame are a pairof case stacking guides 150 and 152, each generally L-shaped in crosssection and which extend beyond the height to which the cases are to bestacked. Mounted at the upper end of one of the guides is switch LS-6,the actuating arm 154 of which is contacted by the top case of thesta-ck as the elevator is raising the entire stack to place it on thecase supports. Upon actuation of LS-6, cylinder 122 is reverselypressurized and instead of continuing to raise the stack, the elevatorreturns it to conveyor 22 to be carried thereby out of the machine. LS-6also serves to reversely pressurize cylinders 82 and 84 of the caselocators, causing retraction of the locators out of the path of thestack so that the stack may leave the machine. As the stack leaves themachine and clears the locators 74 and 76, it trips switch LS-S, whichcauses pressurization of cylinders 82 and 34 to extend the locators andreversely pressurize cylinder 58 to allow the next case to enter themachine so the stacking cycles may continue.

FIGS. 7 and 8 are schematic views of the electrical control system ofthe machine with FIG. 7 relating primarily to the circuitry of suchsystem operative when case stacking is selected. FIG. 8 shows thecircuitry =op erative when unstacking is selected. A selector switch160, when moved to the position shown in FIG. 7, will energize thecircuit of YFIG. 8 for unstacking operation of the machine, and whenmoved to the right to the phantom outline position shown, willde-energize the circuit of FIG. 8 and energize that portion of thecircuit of FIG. 7 below the switch for stacking operation of themachine. As mentioned hereinabove the elevator, case locators, casestop, and case retaining mechanism are operated by uid pressure. Suchpressure is derived from a suitable pump driven by an electric motorschematically indicated at 162 lin FIG. 7. Suitable iluid pressure linesextend from the pump driven by electric motor 162 tothe variouscylinders herebefore mentioned which actuate the case elevator, etc.Disposed in the pressure lines between the pump and the cylinders aresolenoid operated spring return valves. The solenoids for the operationof such valves are shown in FIGS. 7 and 8 as at 164 for the' solenoidthat controls the valve which, in turn, controls the extension andretraction ofthe case locators 74 and 76. Each solenoid operated valve,uponv energization of its' respective solenoid, serves to admit fluidpressure to' the associated cylinder to cause extension of the pistonrody of the cylinder, and upon de-energization of the s'olenoidthe valveis spring-returned to a position redirecting luid pressure to thevassociated cylinder to cause retraction of the piston rod associatedtherewith'. The circuits shown in =FIGS. 7 and 8 include the limitsswitches LS-1, LSV-4, etc., hereinabove mentioned. LS-1, shown' in FIG.7, is provided with two throw arms, one being indicated at LS-la and theother at LS-lb. LS--lEL is a norm-ally open throw which is closed by acase entering the machine and contacting the arm 56. LS-lb is a normallyclosed throw which is opened by a case entering the machine and strikingthe actuating' arm S6. It will be noted that whether the throws orswitches are normally open or' normally closed :isv indicated by whetherthe throw arm' is above or below the circuit line in which the switch isschematically shown as connected.

Circuits 7 and 8 include a plurality of relays, the solenoids for whichare enclosed in circles and give CR designations. The respective slaveswitches' which are controlled by relay solenoids are also given CRdesignations followed by a number identifying the switch with theparticular relay solenoid which controls it. As'there may be a number ofenslaved switches controlled' by a single relay solenoid, the variousswitches controlled b y `anypar'ticular relay solenoid are identifiedsuccessively Vby alphabetical sub-scripts. The' circuitry of FIG.y 7also includesa time` delay type of relay indicated at TR-l which, uponenergization for a determined time interval, will cause its enslavedswitch 'PRK-1.a -to be closed. Upon deenergization of TR-l, switch TR-lwill open. Certain of the relay switches, such as CRAGD, `are normallyclosed, i.e., are closed when the controlling relay solenoid isdeenergized, While relay Switches such #as CR-fl,a are normally open andtare closed only when the relay Vsole'noids actuating such switches areenergized. Ay further description of the circuit of FIG. 7 is believedunnecessary as the operation of the machine can be traced through thecircuit.

The structure of the machine thus far described is sufficient to stackcases entering the indexing station and release successive stacks fromthe station for discharge therefrom on the case conveyor 22. Withcertain additions to the structure described, the machine may be made tounstack cases. Reference has heretofore been made to the unstackirigcircuit (FIG. 8) which would be operative during unstacking. With theexception of LS-3, the same limit switches are used during unstacking asare used during stacking but the circuitry in which the switches areoperated differs as will be evident from a consideration of FIGS. 7 and8. Certain additional limit switches are provided when the machine is tobe used for unstacking. It will be apparent that if the machine is to bea dual purpose machine, i.e., one which will both stack and unstack, theadditional switches necessary for the unstacking operation would bepermanently a part of the machine and while they would be actuatedduring certain phases of the stacking operation, would have no effect onthe stacking operation.

In FIG. 1 la case stop similar to the case stop 58 heretofore describedis secured to the right-hand end of the machine `for the purpose ofpreventing or allowing entry of stacks of cases moving on conveyor 22toward the machine. Such case stop is of identical construction to thatof the one heretofore described and therefore a further description isbelieved unnecessary.

One additional structural addition to the stacking machine to adapt itfor unstackingis the case clamping mechanism 50 shown in FIGS. 3 and 4.Such mechanism includes a pair of clamping pads 166 and 168, onedisposed at each side of -a stack of cases in the machine and extensibleand retractable to grip or release a case disposed between them. Suchcase gripping clamps are Yoperable synchronously with the operation ofthe oase supporting finger mechanism 48 during unstacking operation in amanner hereinafter described. Because the clamping pad 166 is carried bymechanism which is a duplicate of that supporting the pad 168, adescription of the mechanism for pad 166 will suiice for both.

As shown in FIGS. 3 and 4, pad 166 is carried by a pair of push rods 170 and 172, which yare received within rod supporting blocks or the like174 and 176, which are mounted on a plate 178 which extends across thetop of and is secured to the uprights 134 and 136. A hydraulic cylinder180 is mounted on plate 178 with the piston rod 182 thereof connected tothe push rods by a cross member 184. Upon pressurization of cylinder 180in one direction, the push rods and consequently the pad 166 will beextended while upon reverse pressurization, the pad and push rods willbe retracted. The pad moves between the solid outline position shown inFIGS. 3 and 5 and the phantom outline position bearing against a case asshown in FIG. 5 or the solid outline position shown in FIG. 6. Alsoincluded in the machine when adapted 'for unstacking are limit switchesLS9 and LS-dt). Switch LS9 is mounted on a cross member 188 whichextends between and is secured to the bearing blocks -174 'and 176. Theswitch has Ian actuating arm 190` which extends above the pad 166 to apoint where it may be contacted and shifted by a oase disposed betweenthe clamps 166 and 168. Whenever a case is disposed between the clamps,switch LS9 will be actuated. LS9 is schematically shown in the circuitof FIG. 8. Switch LS- is disposed at the left-hand end of the machine tosense the discharge of successive cases from the machine during theunstacking operation and in this respect is similar in function toswitch LS-8 heretofore mentioned in connecton with the stackingoperation. LS-10 includes two throw arms 11S-10a and 11S-10b as shown inFIG. 8, both of which are closed by a case leaving the machine andcontacting the switch actuating arm 192.

The unstacking cycle of the machine occurs as follows. Stacks of casesenter the machine successively on the case conveyor `22, the latterbeing operated in the direction of an arrow U shown in FIG. l. Theselector switch in the control system is shifted to the solid outlineposition shown in FIG. 7 de-energizin-g the circuit of FIG. 7 below theswitch and energizing the circuit of FIG. 8. As the locators 46 are inthe retracted position, the leading stack entering the machine willcontact switch arm 56 to actuate LS-l which, in turn, will energize thecase stop solenoid to extend the stop 66 to prevent the next followingstack from interfering with the leading stack in the machine. As theleading stack moves farther into the machine, one of the cases willstrike the actuating arm 190 of LS9 serving to energize relay CR-10 inturn closing relay switch Clt-10a to energize time delay relay TR-L Uponexpiration of a determined time interval, TR-l will close enslavedswitch TR-la to energize the case elevation solenoid and cause the caseelevator fingers 120 and `128 to lift the stack out of the indexingstation. When the elevator reaches the top of its stroke, it closesswitch LS-4 which, in turn, `causes the elevator to descend. Duringdescent of the elevator and when case VC-2 has reached substantially theposition shown in FIG.

5 during descent of lthe stack, switch LS-11 is closed energizing theclamp solenoid causing fluid pressure to be directed to cylinders 180 ofboth clamping mechanisms to cause extension of the clamps and grippingof case C-2. With case C-2 clamped and with the elevator continuing todescend, case C-1 will continue to descend and will be placed onconveyor 22 for discharge yfrom Vthe machine.

When the elevator bottoms, it closes switch LS-S, which serves toenergize the case support solenoid controlling extension or retractionof the supporting lingers 86 and 86a. These fingers now extend beneathcase C-2 to support it and when they are vfully extended, serve to closeLS-7, which in turn causes the de-energization of the case clampsolenoid causing retraction of the pads 166 and 168. As the first caseto be unstacked leaves the machine and strikes arm 192 of LS-lt), itcloses LS-lt), and 1.840 in turn causing the elevator to re-ascend. Theelevator lifts case C-2 upwardly oif the supporting fingers 86 and 36and when the elevator reaches the top of its stroke, LS-la and LS-fi,Jare closed reversing the movement of the elevator and the cycle repeats.

When the last case of the stack is lowered to the conveyor 22 fordischarge from the machine, as no case will then be in contact withswitch arm `19t), circuit 8 is set up for the reception of the nextstack of cases though the case stop 66a does not retract until the lastcase of the previously unstacked stack of cases clears out of themachine and strikes arm 192 of switch LS-lti. At this point theaforedescribed cycle will repeat.

From the above description it is now apparent that the machine disclosedherein can be used for either stacking or unstacking of cases simply bythe selective positioning of switch 160 in the control system and byselecting the direction of movement of the case conveyor 22. It will benoted that when a stack of cases enters the machine, those cases abovethe lowermost case `will come into contact with the stacking guides l159and 152 which, in this event, serve as case stack locators and interruptthe travel of the stack of cases through the machine. The time delaycycle of time delay relay 'IR-2 may be so adjusted that substantially atthe same instant that a stack of cases entering the machine `cornes intoabutment with guides and 152, the elevator will be caused to ascend tolift the stack olf of the conveyor. It will also be noted that becauseof the particular way in which the machine is cycled during unstacking,the machine will cause unstacking of stacks of cases of varying heightsanywhere from -two or more cases in height. In the event that a singlecase should enter the machine when the machine is operating to unstackcases, such single case will pass directly through the machine withouthindrance.

What we claim is:

1. A case unstacking machine comprising, in combination: an indexingstation, a case conveyor running through the station, case stop means atthe upstream side of said station relative to the movement of the caseconveyor, 'case locating means in the station for interrupting movementof a stack of cases entering the station on the conveyor, a verticallyreciprocable case elevator operable between a stack receiving positionin the station and a stack elevated position above the conveyor, stackretaining mechanism disposed above the conveyor for receiving andholding a stack of cases raised therefrom by the elevator, saidretaining mechanism operable to hold that case superjacent the casesupported by the elevator during lowering of the supported case to theconveyor and responsive to the return of the elevator to a positionsupporting such superjacent case to release such superjaccnt case forlowering to the conveyor and hold the next superjacent case as the stackis lowered on the elevator toward the conveyor, and said case-retainingmechanism comprising case-supporting fingers extensible and retractableadjacent a stack of cases to extend beneath the lowermost case of thestack to support the stack, and further comprising case-gripping pads onopposite sides of a stack of cases and operable synchronously with thesupporting fingers to grip a case prior to the extension of thesupporting fingers therebeneath and release the case upon extension ofthe lingers therebeneath.

2. A case unstacking machine comprising, in combination: a case indexingstation, a case conveyor running through the station, case stackretaining mechanism disposed above the station and including casesupporting means and case clamping means, said case supporting meansincluding extensible and retractable case supporting elements atopposite Sides of a stack of cases spaced above the station andshiftable from a retracted position to an extended position beneath thestack to support the stack thereon when in the extended position, saidclamping means disposed above the case supporting means to grip thesides of a case disposed immediately above the case supporting elements,said clamping means responsive to descent of the elevator to clamp thatcase superjacent the case on the elevator and responsive to an extensionof said case supporting elements beneath the clamped case to release theclamping of the case, and said case supporting means responsive to thepresence of the elevator in a stack supporting position beneath a stackSupported thereby to shift from the extended to the retracted position.

3. A machine for stacking or unstacking cases or the like comprising, incombination: a case conveyor; a case elevator for raising cases from orlowering cases to the conveyor; case-retaining mechanism for holding acase spaced above the conveyor and including rst case-supporting meansshiftable to and from case-supporting positions beneath a case spacedabove the conveyor, and `second case-supporting means operable to gripor release the sides of a case spaced above the conveyor; a selectivecontrol system for stacking or unstacking operation of the machine andoperatively connected to the elevator and retaining mechanism andresponsive, when case stacking is selected, to case-elevating movementof said elevator with a case thereon to cause release of a case held bythe retaining mechanism as the case on the elevator approaches the heldcase, to allow stacking of the cases; and said control systemresponsive, when unstacking is selected, to the presence of the elevatorat a stack-lowering position, to cause said rst case-supporting means ofthe case-retaining mechanism to release the lowest case of the stack andcause the second case-supporting means to grip the sides of thesuperjacent case as the lower case descends on the elevator toward theconveyor, and responsive to a determined descend of the elevatorseparating the case thereon from the case gripped by the retainingmechanism to cause said first supporting means to shift beneath thegripped case to support it.

4. The invention as defined in claim 3 characterized in that when casestacking is selected, said control system is operative to cause releaseof a case held by said retaining mechanism independently of contact ofthe case on the elevator with such retaining mechanism as the case onthe elevator approaches the case held by said retaining mechanism.

References Cited in the le of this patent UNITED STATES PATENTS2,028,410 Rapisarda Jan. 21, 1936 2,550,587 Neja Apr. 24, 1951 2,687,813Verrinder et al Aug. 31, 1954 2,857,040 Campbell Oct. 21, 1958 2,885,097Lyon May 5, 1959 2,931,524 Hallenius Apr. 5, 1960 2,937,482 Layott et alMay 24, 1960 2,997,187 Burt Aug. 22, 1961 FOREIGN PATENTS 530,027Belgium July 15, 1954 1,154,764 France Nov. l2, 1957

